Posts Made By: Ivan Dobrianov

I am not sure that this thread is still "active", but I'll post one more question:

I read that metallic mirror coatings darken with time. Is this true? But they are aupposed to be overcoated with SiO or some other protective layer!? Is it oxygen diffusion through the protective layer that account for this effect?

Isn't there the same problem with all reflecting telescopes [Newtonians and SCTs]?